Antioxidant properties of salmon (Salmo salar L.) protein fraction hydrolysates revealed following their ex vivo digestion and in vitro hydrolysis

BACKGROUND Salmon (Salmo salar L.) myofibryllar protein (MP) and sarcoplasmic protein (SP) were digested with human gastric and duodenal juices and hydrolysed in vitro with commercial pepsin and Corolase PP. RESULTS The digestion after duodenal juice/Corolase PP caused almost complete breakdown of peptide bonds in MP and SP. The DPPH• scavenging activity of proteins decreased during both ex vivo digestion and in vitro hydrolysis. The highest value of DPPH• scavenging activity was shown for the gastric digest of SP (8.88 ± 0.87%). The ABTS+• scavenging activity of MP and SP increased during digestion/hydrolysis. The duodenal digest of SP was characterised by the highest value of ABTS+• scavenging activity (72.7 ± 1.2%). In turn, the highest value of ferric‐reducing power was determined for the gastric digest of SP (84.8 ± 0.2%). Salmon antioxidant peptides Phe‐Ile‐Lys‐Lys, His‐Leu, Ile‐Tyr, Pro‐His‐Leu, Pro‐Trp, Val‐Pro‐Trp were identified in both ex vivo digested and in vitro hydrolysed MP and SP. An antioxidant peptide, Val‐Tyr, was additionally detected in the in vitro hydrolysate of SP. CONCLUSION The results indicate the salmon myofibrillar and sarcoplasmic protein fractions as potential sources of antioxidant peptides that could be released in the gastrointestinal tract but their amino acid sequence and quantification vary. © 2015 Society of Chemical Industry